Articles
Presence of different phenolic groups in various tissues of J. regia
Article number
1420_9
Pages
63 – 68
Language
English
Abstract
Walnuts (Juglans regia L.) are a very high-energy food that is not only rich in valuable nutrients, but also has the most diverse phenolic profile and the highest phenolic content among tree nuts, both in the kernel and in other plant tissues.
In the kernel phenols mainly consist of phenolic acids, flavanols and tannins, and to a lesser extent, tyrosols, dihydrochalcones and flavonols.
In other walnut tissues other phenolic groups can also be found, especially naphthoquinones, of which many are considered toxic.
Since there is little information on the content of phenolic compounds and the relative abundance of different phenolic groups across different walnut tissues, our objective was to compare which phenolic groups are found across different walnut tissues and which are the major phenolic groups in different tissues.
An UHPLC-MS/MS was used to identify more than 150 different phenolic compounds in different walnut tissues.
While no naphthoquinones were found in the edible part of walnut (pellicle and peeled kernels), naphthoquinones were present in all other tissues studied (leaves, petioles, bark, buds, roots and husks), where they act as defensive compounds in allelopathy.
This was expected since juglone and other naphthoquinones are associated with a toxic effect and thus walnut kernels would be potentially toxic if consumed.
Overall naphthoquinones were the major phenolic group found in the leaves, petioles, bark, and buds, hydroxybenzoic acids in side roots, and hydrolysable tannins were the main phenolic compounds identified in the walnut kernels.
The highest content of total analyzed phenolic compounds was in the walnuts main root, followed by side roots and buds, leaves, and 1-year-old bark, while the lowest content was in petioles and 2-year-old bark.
In the kernel phenols mainly consist of phenolic acids, flavanols and tannins, and to a lesser extent, tyrosols, dihydrochalcones and flavonols.
In other walnut tissues other phenolic groups can also be found, especially naphthoquinones, of which many are considered toxic.
Since there is little information on the content of phenolic compounds and the relative abundance of different phenolic groups across different walnut tissues, our objective was to compare which phenolic groups are found across different walnut tissues and which are the major phenolic groups in different tissues.
An UHPLC-MS/MS was used to identify more than 150 different phenolic compounds in different walnut tissues.
While no naphthoquinones were found in the edible part of walnut (pellicle and peeled kernels), naphthoquinones were present in all other tissues studied (leaves, petioles, bark, buds, roots and husks), where they act as defensive compounds in allelopathy.
This was expected since juglone and other naphthoquinones are associated with a toxic effect and thus walnut kernels would be potentially toxic if consumed.
Overall naphthoquinones were the major phenolic group found in the leaves, petioles, bark, and buds, hydroxybenzoic acids in side roots, and hydrolysable tannins were the main phenolic compounds identified in the walnut kernels.
The highest content of total analyzed phenolic compounds was in the walnuts main root, followed by side roots and buds, leaves, and 1-year-old bark, while the lowest content was in petioles and 2-year-old bark.
Publication
Authors
A. Medic, A. Solar, M. Hudina, R. Veberic
Keywords
phenolic compounds, secondary metabolites, tissues, naphthoquinones, quantification, profile
Groups involved
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